- A. wooden piece
- B. plain pins
- C. eraser
- D. a piece of paper
b. Plain pins
- A. Indians
- B. Europeans
- C. Chinese
- D. Egyptians
(c) Chinese
- A. North-east
- B. South-west
- C. East-west
- D. North-south
d. North-South
- A. used
- B. stored
- C. hit with a hammer
- D. cleaned
(c) hit with a hammer
- A. speed
- B. displacement
- C. direction
- D. motion.
c. direction
Oval shape, Disc Shape, cylindrical shape
magnetic materials
magnetic
lodestone
Two
False – A cylindrical magnet has two poles.
True
False – Maximum iron fillings stick in the poles of a bar magnet when it is brought near them.
False – A. compass can be used to find north-south direction at any place.
False – Rubber is a non-magnetic material.
Iron, nails, pins, and needles are magnetic substances because they are attracted to magnets and can be magnetized. Rubber tube is a non-magnetic substance because it is not attracted to magnets and cannot be magnetized. Magnetic substances are typically made of iron or iron-based materials, while non-magnetic substances like rubber, plastic, and wood do not respond to magnetic forces.
Lifts, escalators, and electromagnetic trains use electromagnets in their operation. Electromagnets are temporary magnets created by passing electric current through coiled wire and are essential for these devices to function. Electric bulbs do not use electromagnets; instead, they produce light through the heating of a filament or through other light-emitting mechanisms when electric current passes through them.
The main magnetic properties are attraction, repulsion, and pointing direction. Attraction occurs when a magnet pulls magnetic materials towards it. Repulsion happens when two similar poles of magnets push away from each other. Pointing direction is the property by which a magnet always aligns itself in the north-south direction when freely suspended. Illumination is not a magnetic property as it refers to the emission of light, which is unrelated to magnetism.
Magnetic poles interact with each other in predictable ways. Like poles, such as North-North (N–N) or South-South (S–S), repel each other, meaning they push away from one another. Unlike poles, such as North-South (N–S) or South-North (S–N), attract each other, meaning they pull towards one another. This fundamental principle of magnetism explains how magnets interact and is the basis for many practical applications.
Magnets can lose their magnetic properties through several mechanisms. If a magnet is heated to high temperatures, the thermal energy disrupts the alignment of magnetic domains, causing the magnet to lose its strength. If a magnet is dropped from a height, the impact can disturb the arrangement of magnetic particles and weaken the magnetic force. If a magnet is hit with a hammer or struck forcefully, the physical shock similarly disorganizes the magnetic domains, resulting in loss of magnetism. These three factors demonstrate why magnets must be handled carefully to preserve their magnetic properties.
To magnetize an iron needle, place it on a table in a horizontal position. Take a bar magnet and hold one of its poles near one end of the needle. Rub the magnet along the length of the needle from one end to the other in a single direction without reversing the direction of the magnetic pole. Repeat this stroking process 30 to 40 times, always moving in the same direction. This repeated unidirectional stroking aligns the magnetic domains within the iron needle, causing it to become magnetized. After completing the process, test the magnetized needle by bringing it near iron filings or small pins to verify that it attracts them. If the attraction is weak, continue the magnetization process for additional strokes until the needle develops sufficient magnetic strength to attract pins or iron filings effectively.
Electromagnets are used in electromagnetic trains.
Electromagnets are magnetised when current flows through them. When the direction of the current is changed, poles will be changed.
Magnets are attached at the bottom of the train and rail tracks.
The train is lifted from track up to 10 cm height by the property of the same poles repel each other.
By using attraction and repulsion at the same time between the magnets in tracks and bottom of train move forward.
The magnets are controlled by electricity.
There is no friction. So the train can easily attain a speed of 300 km/ h.
To identify the poles of an unlabelled bar magnet using iron filings, place the bar magnet on a surface and sprinkle iron filings around it. A large number of iron filings will stick to the two ends of the bar magnet, indicating the locations of the poles. The poles are the regions where the magnetic force is concentrated and strongest. The poles attract significantly more iron filings compared to the middle section of the magnet because the magnetic field is most intense at the poles. The poles have the highest magnetic strength, which is why they attract a dense cluster of iron filings. In contrast, the central region of the magnet has a much weaker magnetic field and attracts fewer iron filings. This difference in the concentration of iron filings clearly shows which parts of the magnet are the poles and demonstrates that magnetic force is not uniformly distributed throughout the magnet but is concentrated at the poles.
To remove pins from a glass of water without dipping your hands into the water, take a bar magnet and tie it securely with a thread. Lower the tied magnet into the glass of water containing the pins. The magnetic force will attract the pins, causing them to stick to the magnet. Once the pins are attached to the magnet, carefully pull the magnet out of the water by the thread. The pins will remain attached to the magnet as it is lifted from the water. Finally, collect the pins from the magnet by removing them from its surface. This method allows you to retrieve the pins without getting your hands wet.
- A. Iron
- B. Cobolt
- C. Nickel
- D. Rubber
(d) Rubber
- A. dipped in water
- B. dipped in oil
- C. heated
- D. in freezer
(c) heated
Artificial magnets are magnets that are made by humans through various manufacturing processes, as opposed to natural magnets found in nature. Common examples of artificial magnets include bar magnets, which are rectangular in shape and commonly used in laboratories and classrooms, and horseshoe magnets, which are curved in shape and provide strong magnetic fields at their poles. These man-made magnets are created by magnetizing ferromagnetic materials like iron and are widely used in scientific experiments, educational demonstrations, and practical applications.
There are several different types of artificial magnets available for various applications. Bar magnets are rectangular in shape and are the most commonly used type in schools and laboratories. Horseshoe magnets are curved in shape and provide concentrated magnetic fields at their poles. Ring magnets are circular with a hole in the centre. Needle magnets are small and thin, resembling a needle. Beyond these common types, artificial magnets are also manufactured in other shapes including oval-shaped magnets, disc-shaped magnets, and cylindrical magnets. Each shape is designed for specific applications and purposes, allowing magnets to be used effectively in different scientific, industrial, and everyday contexts.
Substances which are attracted by magnets are called magnetic substances. These materials have the property of being pulled towards a magnet due to their atomic structure. Common examples of magnetic substances include iron, cobalt, and nickel. Iron is the most commonly used magnetic substance and is found in many everyday objects. Cobalt and nickel are also ferromagnetic materials that respond strongly to magnetic fields. When these substances are brought near a magnet, they experience a force of attraction and can themselves become magnetized.
Substances which are not attracted by magnets are called non-magnetic substances. These materials do not respond to magnetic forces and cannot be magnetized under normal circumstances. Common examples of non-magnetic substances include paper, plastic, wood, glass, rubber, and cloth. Non-magnetic substances lack the atomic properties necessary to interact with magnetic fields. Even when placed very close to a magnet, these materials show no attraction or repulsion. Understanding the difference between magnetic and non-magnetic substances helps us identify which materials can be separated using magnets in practical applications.